1. Field of the Invention
The present invention relates to a non-aqueous electrolyte secondary battery and particularly, to a structure of the non-aqueous electrolyte secondary battery having a rolled body therein.
2. Description of the Prior Art
In order to derive a large electric current from a non-aqueous electrolyte secondary battery, it is necessary to reduce an inner resistance due to electric leads. Therefore, it is also necessary to connect a plurality of electric leads with a rolled body to derive an electric current therefrom. In addition, in order to draw out these electric leads, it is necessary to define a gap between the rolled body and the bottom of a case and another gap between the rolled body and a header.
However, in a conventional non-aqueous electrolyte secondary battery, a structure as shown in FIG. 4 which is disclosed in JPA 9-259857 is popular. Referring to FIG. 4, although recess 204 is formed on the upper side of case 201, the purpose of forming recess 204 is not to hold rolled body 200 but to have recess 204 function as a receiver of a stress caused when caulking case 201 with header 203 to seal case 201.
In the conventional non-aqueous electrolyte secondary battery, rolled body 200 is merely enclosed in case 201, and there are free spaces over and under rolled body 200. Therefore, rolled body 200 may move freely inside case 201. Thus, when using the conventional non-aqueous electrolyte secondary battery, a relative position of rolled body 200 with respect to case 201 varies by vibration, and stresses are applied to both terminals of a plurality of negative electrode leads (not shown) connecting a lower terminal of rolled body 200 with a bottom of case 201 and terminals of a plurality of positive electrode leads (not shown) connection an upper terminal of rolled body 200 with header 203, resulting in that at least parts of these leads are disconnected and an inner resistance due to leads increases. In addition, when parts of positive electrode leads are disconnected, the disconnected leads contact with case 201, resulting in short circuit.
In order to overcome the aforementioned disadvantages, the present invention has been made and accordingly, has an object to provide a non-aqueous electrolyte secondary battery in which a rolled body does not relatively move with respect to a case.
According to an aspect of the present invention, there is provided a non-aqueous electrolyte secondary battery which comprises: a case comprising a bottom and a sidewall; a rolled body comprising: a positive electrode comprised of a first electric plate and a positive electrode active material applied on the first electric plate; a negative electrode comprised of a second electric plate and a negative electrode active material applied on the second electric plate; and a separator inserted between the positive electrode and the negative electrode; wherein the rolled body is formed by laminating and rolling the positive electrode, the negative electrode, and the separator; and the rolled body is enclosed in the body; non-aqueous electrolyte enclosed in the case; a header used for sealing the case; a plurality of positive electrode leads connecting the positive electrode with the header; a plurality of negative electrode leads connecting the negative electrode with a bottom of the case; and holding means for holding the rolled body so that the rolled body does not relatively move with respect to the case while keeping a gap between a lower terminal of the rolled body and the bottom of the case and a gap between an upper terminal of the rolled body and the header.
In the non-aqueous electrolyte secondary battery, the holding means may comprise: a first recess at least partially formed in the neighborhood of an upper end of the sidewall of the case; and a second recess at least partially formed in the neighborhood of a lower end of the sidewall of the case;
wherein the first recess and the second recess hold the rolled body.
In the non-aqueous electrolyte secondary battery, the holding means may comprise: a first recess at least partially formed in the neighborhood of an upper end of the sidewall of the case; and a short-diameter portion formed in the neighborhood of a lower end of the sidewall of the case; wherein the first recess and a shoulder of the short-diameter portion hold the rolled body.
In the non-aqueous electrolyte secondary battery, the holding means may comprise: a first recess at least partially formed in the neighborhood of an upper end of the sidewall of the case; and a spacer disposed between the bottom of the case and the lower terminal of the rolled body; wherein the first recess and the spacer hold the rolled body.
The non-aqueous electrolyte secondary battery may further comprise: a spacer disposed between the first recess and the rolled body.
The non-aqueous electrolyte secondary battery may further comprise: an insulator disposed between the rolled body and the holding means.
These and other objects, features and advantages of the present invention will become more apparent in the light of the following detailed description of the best mode embodiments thereof, as illustrated in the accompanying drawings.